# Thread: what does e^x mean?

1. ## what does e^x mean?

for something like this: 12e^x-20=0 how do i find x?

2. i guess i'm answering my own question but i'm assuming i take the ln of both sides so essentially it would be ln (40/12) which is 1.2039?

3. Originally Posted by frozenflames
for something like this: 12e^x-20=0 how do i find x?
Do you realize that you posted this question in the Pre-Calculus forum?
Are you doing a course in Pre-Calculus?
If so, surely you know what $\displaystyle e^x$ means.

4. Originally Posted by frozenflames
i guess i'm answering my own question but i'm assuming i take the ln of both sides so essentially it would be ln (40/12) which is 1.2039?
This is correct, but like Plato said your thread title is strange. $\displaystyle e$ is just a number, so $\displaystyle e^x$ is $\displaystyle (e*e*e*e...)$, x times.

5. Originally Posted by frozenflames
for something like this: 12e^x-20=0 how do i find x?
Originally Posted by frozenflames
i guess i'm answering my own question but i'm assuming i take the ln of both sides so essentially it would be ln (40/12) which is 1.2039?
If you post your working that led to this answer then your error can be explained (because this answer is wrong).

6. Originally Posted by mr fantastic
If you post your working that led to this answer then your error can be explained (because this answer is wrong).
Spoiler:
$\displaystyle 12e^x-20=0$

$\displaystyle 12e^x=20 \Rightarrow e^x=\frac{20}{12}$

$\displaystyle \ln(e^x)=\ln(\frac{20}{12}) \Rightarrow x\ln(e)= \ln(\frac{20}{12})$

I get the same answer as OP. What did I do wrong?

7. Originally Posted by Jameson
Spoiler:
$\displaystyle 12e^x-20=0$

$\displaystyle 12e^x=20 \Rightarrow e^x=\frac{20}{12}$

$\displaystyle \ln(e^x)=\ln(\frac{20}{12}) \Rightarrow x\ln(e)= \ln(\frac{20}{12})$

I get the same answer as OP. What did I do wrong?
What you got (and which is correct) is
Spoiler:
$\displaystyle x = \log_e \frac{20}{12}$

This is not the same as $\displaystyle \log_e \frac{40}{12}$ (which is what the OP got) ....!

8. Oh duh. I misread his answer. Silly me.